A variety of semiconductor chip packages are known that provide support for an integrated circuit chip (IC) or die and associated bond wires, provide protection from the environment, and enable surface mounting of the die to and interconnection with a printed circuit board (PCB). One conventional package configuration includes a lead frame having a die pad and surrounding wire bond (or contact) pads.
Lead frame semiconductor packages are well known and widely used in the electronics industry to house, mount, and interconnect a variety of ICs. A conventional lead frame is typically die-stamped or chemically etched from a sheet of flat-stock metal, and includes a plurality of metal leads temporarily held together in a planar arrangement about a central region during package manufacture by a rectangular frame comprising a plurality of expendable “dam-bars.” A mounting pad (or die pad) for a semiconductor die thereon is supported in the central region by “tie-bars” that attach to the frame. The leads extend from a first end integral with the frame to an opposite second end adjacent to, but spaced apart from, the die pad.
Known challenges to lead frame packaging of semiconductor devices include adhesion of the die attach material, mold compound, and wire bonds to the surface of the lead frame. Known methods of adhesion modification include coating the lead frame surface with an adhesion promoter layer, and global roughening of the lead frame surface using an aggressive electrolytic plating step to provide a plating layer with a large grain structure or a micro-etching step that uses a chemical solution to etch the base material to increase the interfacial area for mechanical locking.